Oil pump structure

ABSTRACT

An oil pump is adapted to pump oil by utilizing the variation of a cavity formed between mutually inwardly engaging gear-teeth of a drive gear and a driven gear. An oil pressure relief groove has a certain shape and is disposed at an isolated portion of the oil pump housing between an oil intake groove and an oil discharge groove. The oil pressure relief groove is in fluid communication with the oil discharge groove and relieves pressure of the oil as it is compressed between the teeth of the gears.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of Korean Application No. 10-2003-0031573, filed on May 19, 2003, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] Generally, the present invention relates to an oil pump with a drive gear and a driven gear. More particularly the drive gear and driven gear both comprise parachoid-shaped teeth that inwardly engage each other without the aid of a crescent and an oil pump housing that includes an oil pressure relief groove.

BACKGROUND OF THE INVENTION

[0003] In conventional oil pumps, an inner drive gear is typically formed with one less gear-tooth than an outer driven gear. When the drive gear and the driven gear engage each other and spin, the drive gear rotates one gear-tooth faster than the driven gear per cycle. During the execution of a single complete cycle or revolution of the drive gear, a cavity is formed between the drive gear-teeth and the driven gear-teeth. The cavity gradually and consecutively expands and contracts as the drive gear and driven gear rotate.

[0004] The typical oil pump also includes a housing that has an oil intake groove, an oil discharge groove, and an isolated housing portion. Theoretically, oil is taken up between teeth of the drive gear and driven gear and compressed into a cavity between these teeth. Initially the cavity is in an expended state, the cavity between the drive gear and the driven gear then contracts as the gears rotate and discharge the oil into the oil discharge groove. Thus, the oil is taken in from the oil intake groove, compressed between the teeth of the drive gear and driven gear and delivered to the oil discharge groove.

[0005] Typically, the end portion of the oil intake groove and the start portion of the oil exhaust groove are configured to be separated by approximately 12 degrees. An isolated housing portion is disposed between the oil intake and oil discharge grooves across this 12 degree span. A drawback in the typical oil pump design is that this approximately 12 degree angle the cavity between the gear-teeth contracts and the oil between the gear-teeth becomes extremely compressed thereby, lowering the durability of the housing and increasing oil leakage through clearance between the meshing gear-teeth.

SUMMARY OF THE INVENTION

[0006] An embodiment of the oil pump structure of the present invention is provided to prevent deterioration of the durability of the oil pump. Oil pump durability is deteriorated while the gear-teeth of the drive gear and driven gear pass through the isolated portion of a housing and the oil between the gear-teeth becomes extremely compressed. The present invention also assists in reducing oil leakage through clearance between the gear-teeth.

[0007] In an preferred embodiment of the present invention, the oil pump structure comprises an oil pressure relief groove formed in the isolated portion to communicate with the oil discharge groove. The oil pressure relief groove has a start portion positioned where a contact point of the gear-teeth is projected onto the isolated portion. The contact point is where the gear-teeth make contact at the oil discharge groove side thereby forming the maximum cavity between the gear-teeth mutually and inwardly engaging. The isolated portion is formed at a housing for isolating the oil intake groove and the oil discharge groove.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which:

[0009]FIG. 1 illustrates an inside of an oil pump showing a drive gear and a driven gear according to an embodiment of the present invention;

[0010]FIG. 2 illustrates an inner side of an oil pump housing with the drive gear and the driven gear of FIG. 1 removed; and

[0011]FIG. 3 illustrates the components of FIGS. 1 and 2 enlarged in a working relationship according to an embodiment of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0012] Referring to FIG. 1, a driven gear 3 is installed inside a housing 1, and a drive gear 5 is mounted at an inner side of the driven gear 3. The driven gear 3 and drive gear 5 engage each other at a lower side of the drawing. In operation, when the drive gear 5 rotates, the driven gear 3 correspondingly rotates in a counter-clockwise direction. In reference to the drawing, as the drive gear 5 and driven gear 3 rotate, the drive gear 5 and driven gear 3 change their dispositions from the state represented by the alternating long and short dash lines to the position represented by the solid lines of FIG. 1.

[0013] In the position represented by the letter “A” in FIG. 1, two gear-teeth of the drive gear 5 and two gear-teeth of the driven gear 3 are symmetrically placed and a cavity (S) is formed between the four gear-teeth. At this position, the cavity (S) is at a maximum volume. As the drive gear 5 and driven gear 3 spin in the counterclockwise direction, the gears and respective cavity formed there-between change from state “A” to state “B”, as shown in FIG. 1 by the solid lines. In the position B, the oil in the cavity starts to become compressed as the volume of the cavity decreases.

[0014]FIG. 2 illustrates an inside of the housing 1 with the drive gear 5 and the driven gear 3 removed. An oil intake groove 7 is shown at the right side of the figure, while an oil discharge groove 9 is shown at the left side of the figure. An isolated portion 11 separates the oil intake groove 7 and oil discharge groove 9 by being disposed therebetween. The isolated portion 11 is formed with an oil pressure relief groove 13.

[0015] According to FIG. 3, a start portion 15 of the oil pressure relief groove 13 is situated where a contact point (P) of the gear-teeth is projected onto the isolated portion 11. The contact point (P) is adjacent the oil discharge groove side of the gear-teeth when the gear-teeth form a maximal cavity, such as at state “A” of FIG. 1. The cross-section of the oil pressure relief groove 13 is configured to gradually expand from the start portion 15 to the oil discharge groove 9. In other words, the cross-section of the oil pressure relief groove 13 is configured to gradually converge to zero from the oil discharge groove 9 toward the oil intake groove 7 at the start portion 15. Therefore, when the gear-teeth form a maximum cavity, such as in state “A”, the oil cannot flow through the oil pressure relief groove 13. However, once the gear-teeth rotate beyond state “A”, the cavity formed there between becomes in fluid communication with the oil pressure relief groove 13 and oil starts to flow into the oil discharge groove 9 via the oil pressure relief groove 13.

[0016] As a result, when the gear-teeth of the drive gear 5 and driven gear 3 pass through the isolated portion 11 of the housing 1 and the cavity between the gear-teeth starts to reduce immediately after forming a maximum cavity, the oil from the cavity between the gear-teeth may begin to be released into the oil discharge groove 9 via the oil pressure relief groove 13. The oil pressure relief groove 13, thus, contributing to a prevention of the deterioration of the durability of the oil pump, which occurs when an excessive pressure is applied onto the housing 1, and a prevention of oil leakage through the clearance between the gear-teeth. 

What is claimed is:
 1. An oil pump structure, comprising: an oil pressure relief groove formed at an isolated portion of an oil housing, said oil pressure relief groove communicating with an oil discharge groove and having a start portion where a contact point between teeth of a drive gear and teeth of a driven gear is projected onto said isolated portion, and wherein said contact point is contact between gear-teeth at the oil discharge groove side of the gear-teeth when the gear teeth mutually and inwardly engage to form a maximum cavity, and said isolated portion is configured and dimensioned for isolating an oil intake groove from said oil discharge groove.
 2. The structure as defined in claim 1, wherein the cross-section of said oil pressure relief groove is configured to gradually expand from said start portion to said oil discharge groove.
 3. The structure as defined in claim 1, wherein the cross-section of said oil pressure relief groove is configured to gradually converge to zero from said oil discharge groove to said start portion.
 4. An oil pump structure, comprising: a housing defining an oil intake groove and defining an oil discharge groove; an isolated portion disposed between the oil intake groove and the oil discharge groove, wherein said isolated portion maintains oil discretely in the respective grooves; and wherein said isolated portion defines an oil pressure relief groove, said oil pressure relief groove configured and dimensioned in fluid communication with said oil discharge groove.
 5. The oil pump of claim 4, wherein said oil pressure relief groove tapers to an end point with a zero cross-sectional diameter from said oil discharge groove toward said oil intake groove.
 6. The oil pump of claim 5, wherein said end point is positioned toward said oil discharge groove from a position where a drive gear and a driven gear form a cavity between respective teeth of the gears.
 7. The oil pump of claim 6, wherein said oil pressure relief groove is configured in an arc that corresponds to an arc formed by rotation of the cavity such that as the cavity rotates over the oil pressure relief groove oil maintained within the cavity enters the oil pressure relief groove.
 8. An oil pump structure, comprising: a housing defining an intake groove and a discharge groove, said intake groove and said discharge groove being separated by an isolate portion of the housing; and said isolate portion of the housing being configured and dimensioned to define an oil pressure relief groove, said oil pressure relief groove is in fluid communication with said oil discharge groove and extends to an end point toward said oil intake groove, wherein said end point is configured adjacent a position where teeth of a drive gear and teeth of a driven gear mesh to form an initial cavity. 